1. Field of the Invention
The present invention relates to an electrochromic mirror or window capable of displaying information using an electrochromic display (ECD).
2. Description of the Prior Art
Generally, an electrochromic display (ECD) is a non-emissive display capable of adjusting the color of an electrochromic material through controlling the chemical reaction of the electrochromic material by applying an electric signal to the electrochromic material.
Such an ECD is applied to a smart mirror or a smart window. The smart mirror is used as a rear view mirror of a vehicle. If strong light is applied thereto from behind of the vehicle, the smart mirror is automatically colorized thereby preventing glare. When the smart window is utilized as an external window of a building, the smart window can adjust transmittance of sunlight so that it is possible to save heating/cooling energy for the building. In addition, the smart window can be used as a unique interior decoration electrically controlling an exposed space inside of the building. However, the conventional ECD simply serves as a mirror or a window for adjusting reflectivity or transmittance of light using an electrochromic material.
FIG. 1 is a schematic view illustrating a basic structure of an ECD including a solid-phase electrochromic material provided on an electrode in the form of an electrochromic layer. Referring to FIG. 1, the ECD 1 includes a lower electrode 11 formed on a first glass substrate 10, an upper electrode 15 formed on a lower surface of a second glass substrate 16 while facing the lower electrode 11 and spaced away from the lower electrode 11 by a predetermined distance, an electrochromic layer 14 formed on a lower surface of the upper electrode 15 and including an electrochromic material changing its color depending on an electric signal applied thereto, an electrolyte layer 13 formed on a lower surface of the electrochromic layer 14 and including ions related to the electrochromic reaction, and an ion storage 12 formed on a lower surface of the electrolyte layer 13 for storing ions having polarity opposite to that of the ions related to the electrochromic reaction. Generally, at least one of the lower and upper electrodes 11 and 15 is a transparent electrode, such as indium tin oxide (ITO) electrode. The ion storage 12 can be omitted and the electrolyte layer 13 can be replaced with an ionic liquid layer including ionic liquid.
If voltage is applied to the ECD 1, current flows from the electrochromic layer 14 to the ion storage 12, thereby coloring the electrochromic layer 14. In contrast, if the current flows from the ion storage 12 to the electrochromic layer 14, the electrochromic layer 14 is decolored. The above coloring and decoloring reactions of the electrochromic layer 14 may also occur with the current flow inverse to the above current flow depending on materials of the electrochromic layer 14.
If the upper electrode 15 is a transparent electrode and the lower electrode 11 is a metal electrode (other elements are assumed as transparent elements), the ECD 1 shown in FIG. 1 can be used as a smart mirror capable of electrically adjusting reflectivity of light. In the meantime, if the upper and lower electrodes 15 and 11 are transparent electrodes (other elements are assumed as transparent elements), the ECD 1 shown in FIG. 1 can be used as a smart window capable of electrically adjusting transmittance of light.